The invention relates to sputtering targets and methods of making same; and to sputtering targets of high purity metals and alloys. Among these metals are Al, Ti, Cu, Ta, Ni, Mo, Au, Ag, Pt and alloys thereof, including alloys with these and or other elements. Sputtering targets may be used in electronics and semiconductor industries for deposition of thin films. To provide high resolution of thin films, uniform and step coverages, effective sputtering rate and other requirements, targets should have homogenous composition, fine and uniform structure, controllable texture and be free from precipitates, particles and other inclusions. Also, they should have high strength and simple recycling. Therefore, significant improvements are desired in the metallurgy of targets especially of large size targets.
A special deformation technique known as equal channel angular extrusion (ECAE) described in U.S. Pat. Nos. 5,400,633; 5,513,512; 5,600,989; and U.S. Pat. No. 5,590,389 is used with advantage in accordance with the invention. The disclosures of the aforementioned patents are expressly incorporated herein by reference.
The invention relates to a sputtering target made by a process including casting. The target has a target surface such that the surface of the target subjected to sputtering (referred to as target surface) has a substantially homogeneous composition at any location, substantial absence of pores, voids, inclusions and other casting defects, grain size less than about 1 xcexcm and substantially uniform structure and texture at any location. Preferably, the target comprises at least one of Al, Ti, Cu, Ta, Ni, Mo, Au, Ag, Pt and alloys thereof.
The invention also relates to a method of manufacturing a target, as described above. The method comprises fabricating an article suitable for use as a sputtering target comprising the steps of:
a. providing a cast ingot;
b. homogenizing said ingot at time and temperature sufficient for redistribution of macrosegregations and microsegregations; and
c. subjecting said ingot to equal channel angular extrusion to refine grains therein.
More particularly, a method of making a sputtering target comprising the steps of:
a. providing a cast ingot with a length-to-diameter ratio up to 2;
b. hot forging said ingot with reductions and to a thickness sufficient for healing and full elimination of case defects;
c. subjecting said hot forged product to equal channel extrusion; and
d. manufacturing into a sputtering target.
Still more particularly, a method of fabricating an article suitable for use as a sputtering target comprising the steps of:
a. providing a cast ingot;
b. solutionizing heat treating said cast ingot at temperature and time necessary to dissolve all precipitates and particle bearing phases; and
c. Equal channel angular extruding at temperature below aging temperatures.
After fabricating as described to produce an article, it may be manufactured into a sputtering target.